1. Field of the Invention
The present invention relates to screen door frames and window screen frames and a method of manufacturing such frames.
2. Description of the Prior Art
In conventional practice metal screen door frames and metal window screen frames are manufactured from strips of flat metal stock which are die cut to form angled miter corners and opposing flaps which are later adhesively secured at the corners of the frame. According to conventional practice a continuous flat sheet metal strip is advanced using a conveyor system beneath one or more dies mounted thereabove. The sheet metal strip is advanced a distance equal to the length of metal stock needed to form a jamb and an adjacent head or a sill of a single screen frame and then halted beneath the dies. The dies are thereupon actuated and are brought down onto the flat sheet metal strip to cut angled mitered corners and opposing flaps in longitudinal edges of the strip. The dies are then raised from the flat sheet metal strip out of contact therewith.
The flat sheet metal strip is then advanced another incremental length equal to the length necessary to form another of the jambs and a head or sill of the screen frame. The sheet metal strip is thereupon again halted and the die cutting operation is thereupon repeated. A conventional screen frame fabrication technique of this type is described in my prior U.S. Pat. No. 5,018,263.
In the prior die cutting or stamping technique described, the flat sheet metal strip used to form the screen frame is advanced in incremental steps and then halted so that it remains stationary beneath the cutting dies as the dies are actuated to strike the sheet metal strip and cut the necessary mitered corners and opposing flaps into the edges thereof. Because of the finite time that is required for the die blades to contact the surface of the metal strip, penetrate through the structure thereof, and withdraw from contact with the metal strip, it has heretofore been considered necessary to immobilize the sheet metal strip beneath the dies for the length of time that is required to advance and withdraw the dies through the structure of the sheet metal strip. Cyclical advancement and halting of the sheet metal strip has heretofore been required so that the dies cut cleanly and at precise intervals along the length of the strip. Utilizing this technique a throughput of approximately 900 one-piece screen door frames can be produced per working shift.